MIS375 L06 Ch06 ProjNetwork [Compatibility Mode]
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Transcript of MIS375 L06 Ch06 ProjNetwork [Compatibility Mode]
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THE MANAGERIAL PROCESSTHE MANAGERIAL PROCESS Clifford F. GrayEric W. Larson
Third Edition
Clifford F. GrayEric W. Larson
Third EditionProjectManagementrojectManagement
Chapter 6Chapter 6
Developing a Project PlanDeveloping a Project Plan
Developing the Project PlanDeveloping the Project Plan
The Project Network
A tool used for planning, scheduling, monitoring project progress
Time, Cost, Performance
A graphic flow chart of the project plan
Depicts the project activities as well as their logical sequences,
interdependencies, and start and finish times.
Identifies the longest path through the network -the critical path
Use networks for non-trivial projects
Networks are displayed in universal formats
Easy to modify
Easy to update
Developing the Project PlanDeveloping the Project Plan
The Project Network
A roadmap
Provides the basis for scheduling labor and equipment
Enhances communication among project participants Provides a basis for budgeting cash flow
Provides an estimate of the entire projects duration
Highlights activities that are critical and can not be delayed
Identifies activities that can be delayed
Shows duration, start and finish times of individual activities
Minimizes surprises
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Network BasicsNetwork Basics
Activity: an element in the project that consumes time Work or wait
WBS Work acka es are used to build activities
An activity can be 1 or more work packages
Activities are placed in a sequence that provides for orderlycompletion of the project
Networks are built using nodes and arrows
Two Approaches
Activit -on-Node (AON)
Uses a node to depict an activity.
Activity-on-Arrow (AOA)
Uses an arrow to depict an activity.
Network BasicsNetwork Basics
Integration of WBS and Network is sometimesoverlooked, but many times crucial
De endenc timin se uencin of work acka es are not art,
,
of WBS
P.147
Manager derives activity time estimates from work package task
times
From Work Package to NetworkFrom Work Package to Network
WBS/Work Packages to Network
FIGURE 6.1
Constructing a Project NetworkConstructing a Project Network
Terminology
Activity: an element of the project thatrequ res me, u no necessar yresources
Usually one or more work package tasks
Merge Activity: an activity that has two ormore preceding activities on which it
B D
Parallel (Concurrent) Activities: Activities
that can occur independently and, ifdesired, not at the same time.
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Constructing a Project Network (contd)Constructing a Project Network (contd)
Terminology
Path: a sequence of connected, dependent activities.
Critical path: the longest path through the activity network that
allows for the completion of all project-related activities; theshortest expected time in which the entire project can becompleted. Delays on the critical path will delay completion of theentire project.
C
A B D
(Assumes that minimum of A + B > minimum of C in length of times to complete activities.)
Constructing a Project Network (contd)Constructing a Project Network (contd)
TerminologyEvent: a point in time when an activity is started or completed. It
does not consume time.
Burst Activity: an activity that has more than one activity
immediately following it (more than one dependency arrowflowing from it).
B
D
A C
Basic Rules to Follow in DevelopingBasic Rules to Follow in DevelopingProject NetworksProject Networks
Networks typically flow from left to right.
An activity cannot begin until all of its preceding activities arecomplete.
Arrows indicate precedence and flow and can cross over each other(Arrow length and angle are arbitrary for drawing convenience).
Identify each activity with a unique number; this number must be
greater than its predecessors.
Loopin is not allowed.
Conditional statements are not allowed (Ifthen)
Use single project start and stop nodes.
P.149
Basic RelationshipsBasic Relationships
Predecessor
An activity that must be completed immediately before an activity
Which activities must come immediatel before this activit ?
Successor An activity that must immediately follow an activity
Concurrent / Parallel
An activity that can occur while another activity is taking place
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ExampleExample
P. 151
raw ng e ne wor p aces e ac v es n e correcsequence
Once the network is completed we can calculate thetimes (dates) for completion for each activity as well asthe projects critical path
This is done by passing through the project
Network Computation ProcessNetwork Computation Process
Forward PassEarliest Times How soon can the activity start? (early startES)
How soon can the project finish? (expected timeET)
Backward PassLatest Times
How late can the activity start? (late startLS)
How late can the activity finish? (late finishLF)
Which activities represent the critical path?
How long can non-critical activities be delayed? (slack or floatSL)
Forward Pass ComputationForward Pass Computation
Starting with the first activity
add activity times along each path in the network
ES + Duration = EF
Carry the early finish (EF) to the next activity where itbecomes its early start (ES) unless
The next succeeding activity is a merge activity, in whichcase the largest EF of all preceding activities is selected
Do a forward pass on Koll Business Center
Backward Pass ComputationBackward Pass Computation
Starting with the early finish time of the last activity
The early finish becomes the late finish of the last activity
Subtract duration for that activity to get its late start
LF - Duration = LS
Carry the late start (LS) to all predecessors where itbecomes its (their) late finish (LF) unless
The next preceding activity is a burst activity, in whichcase the smallest LF of all preceding activities isselected.
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Determining Slack (or Float)Determining Slack (or Float)
Slack (or Float) The amount of time an activity can be delayed after the start of a longer
parallel activity or activities, thereafter delaying the entire project
Can be positive, zero, negative
The critical path is the network path(s) that has (have) the leastslack in common.
Zero slack (unless an imposed finish date exists)
Total Slack: Slack of the total pro ect
Free Slack: Amount of slack along an activity or chain of activitiesavailable without delay to the project
Critical ActivitiesCritical Activities
Mark critical path with heavy dashed arrows Critical activities represent approximately 10% of the
Close attention must be paid to critical activities soproject is not delayed
Slack / Critical Path NotesSlack / Critical Path Notes
Delaying activities with slack will impact the availabilityof slack for downstream activities
assign resources
Keep very close eyes on the critical path items, as theywill delay your project
Shortening a schedule requires adding resources to acritical activity. Choose the activity that costs the leasto s or en
Practical ConsiderationsPractical Considerations
Level of detail
As appropriate (project, cost, culture)
No conditional logic
No Looping
Activity Numbering
Predecessors should always be lower than their successors
Computer programs can do this
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Practical ConsiderationsPractical Considerations
Use of computers to develop networks Pert (Program Evaluation and Review Technique)
Gantt Bar Charts Henr Laurence Gantt 1861-1919 ,
P.163
Calendar dates need to be assigned
Weekends, holidays
Extended Network TechniquesExtended Network Techniquesto Come Close to Realityto Come Close to Reality
Start-Finish is not always the way activities really work.
Laddering (overlapping)
Activities can be broken into segments so the following activitycan begin sooner and not delay the work
e.g., Laying pipe (p.164)
Extended Network TechniquesExtended Network Techniquesto Come Close to Realityto Come Close to Reality
Lags (also overlapping) The minimum amount of time a dependent activity must be
delayed to begin or end.
Lengthy activities can be broken down to reduce the delay in thestart of successor activities.
Lags can be used to constrain finish-to-start, start-to-start, finish-to-finish, start-to-finish, or combination relationships.
Can be used to sandbag be careful
Finish-to-Start
Start-to-Start
Finish-to-Finish (p.168)
Start-to-Finish
Hammock ActivitiesHammock Activities
Hammock Activity
An activity that spans over a segment of a project.
Duration of hammock activities is determined after the networkplan is drawn.
Hammock activities are used to aggregate sections of the projectto facilitate getting the right amount of detail for specific sections
of a project.